Investigation of electro-discharge micro-machining of titanium super alloy

Being a difficult-to-cut material, titanium alloy suffers poor machinability for most cutting processes, especially the drilling of micro-holes using traditional machining methods. Although electrical discharge machining (EDM) is suitable for machining titanium alloys, selection of machining parameters for higher machining rate and accuracy is a challenging task in machining micro-holes. The present research attempts to optimize micro-EDM process parameters for machining Ti-6Al-4V super alloy. To verify the optimal micro-EDM process parameters settings, metal removal rate (MRR), tool-wear rate (TWR), over cut (OC) and taper were chosen as observed performance criteria. In addition, four independent parameters such as peak current, pulse-on time, flushing pressure, and duty ratio were adopted for evaluation by the Taguchi method. From the ANOVA and S/N ratio graph, the significant process parameters and the optimal combination level of machining parameters were obtained. It is seen that machining performances are affected mostly by the peak current and pulse-on time during micro-electro-discharge machining of titanium alloy. Mathematical models have been developed to establish the relationship between various significant process parameters and micro-EDM performance criteria. In-depth studies have also been made to examine the influence of various process parameters on the white layer and surface topography through SEM micrographs of machined micro-hole.